Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
254 AM EDT Thu May 02 2019
Valid 12Z Sun May 05 2019 - 12Z Thu May 09 2019
...Weather Highlights/Threats...
A lead low will lift offshore Sunday into Monday to produce an
area of enhanced rains over the northern mid-Atlantic and Southern
New England. A trailing front back across the Southeast, the Gulf
and the southern Plains will meanwhile remain a focus for local
heavy rain/thunderstorms.
Well upstream, upper ridging will remain anchored over the
northeastern Pacific which will keep drive split flow over the
Lower 48 next week. An unsettling and initially closed southern
stream low will work into California and the Southwest as a series
of cooling and precipitation focusing northern stream systems
skirt along the US/Canadian border.
Expect scattered showers and some convection into the Great
Basin/Rockies. Precipitation (generally rain with high snow
levels) will mostly focus on higher elevations, but some valley
rain. Moisture influx into the region appears to be modest. This
pattern will also favor periods of organized strong convection
with a cell training/excessive rainfall/runoff threat as a series
of hard to time northern and southern stream impulses eject over
the east-central U.S. overtop a building upper ridge over the Deep
South. Systems may be primed to periodically tap deepening
moisture and instability pooled by return Gulf of Mexico inflow
into two surface frontal systems/enhanced baroclinic zones.
...Guidance/Predictability Assessment...
The WPC medium range product suite was composed from a blend of
compatable GFS/ECMWF/UKMET/Canadian model guidance Sunday. Opted
to transition to an ensemble mean based forecast starting Monday
amid growing forecast spread and uncertainty, primarily with
smaller scale impulse timing/interactions and convection genesis.
This maintains good WPC continuity.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml